1. Field of the Invention
This invention relates generally to methods of measuring transistor scattering parameters, and more particularly, to a method of generating transistor scattering parameters using a single circuit simulation with a self-correction scheme for the artificial DC voltage dropped across the 50-Ohm resistor representing transmission line impedance.
2. Description of the Prior Art
The standard approach for generating transistor scattering parameters from a single circuit simulation produces erroneous results because of transistor debiasing caused by the unreal DC voltage dropped across the 50-Ohm resistance that is included to model transmission line impedance in the frequency domain. In view of the foregoing, it would be desirable and advantageous in the art to provide a correction for the problem of debiasing, that is typically, but erroneously ignored. It would further be advantageous to provide an approach to providing the transistor DC characteristics as part of the AC solution using solely one simulation.
The present invention is directed to a method providing for the generation of transistor scattering parameters using a single circuit simulation with a self-correction scheme for the artificial DC voltage dropped across the 50-Ohm resistor representing transmission line impedance. A sub-circuit without 50-Ohm transmission line resistance is used to compute the correct transistor bias currents. This current is used, via a current-controlled voltage source, to compensate for the DC voltage dropped across a 50-Ohm resistor contained in the network that generates device scattering parameters. The single circuit simulation produces both the AC solution and DC solution for simultaneous optimization.
In one aspect of the invention, a single circuit simulation is provided having the capability to retrieve DC measures of the circuit simultaneously with high-frequency RF measures of the circuit.
In another aspect of the invention, a single circuit simulation is provided to simultaneously measure the AC and DC characteristics of a transistor.